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Listening to the Land: How Bioacoustics Monitoring at Duke Farms Helps Us Track Indicator Species 

At Duke Farms, we believe the natural world speaks volumes if you know how to listen. One of the innovative tools we use to understand the health of our ecosystems […]

Written by:

Vaulted Oak

Jul 15, 2025

At Duke Farms, we believe the natural world speaks volumes if you know how to listen. One of the innovative tools we use to understand the health of our ecosystems is bioacoustics monitoring, a method that allows us to “hear” the environment through science. 

Bioacoustics is the study of sounds produced by living organisms. From the chorus of spring peepers (Pseudacris crucifer) in a wetland to the drumming of a Red-bellied woodpecker (Melanerpes carolinus) deep in the forest. At Duke Farms, we use small recorders to collect data across our diverse habitats. We use autonomous recording units (ARUs), which provide a long-term record of ecological change, helping us make data-informed decisions about land stewardship practices and habitat restoration. ARUs are considered a non-invasive way to observe wildlife occurrences.  It enables us to detect elusive or nocturnal species that visual surveys might miss, and record for days at a time.  Meaning, a lot more data without the bias of a surveyor's disturbance when collecting data in the field.  

But how does it actually work? 

Our conservation team carefully installs ARUs in key habitats like wetlands, grasslands, and forests. These devices can record for weeks or months at a time, storing hundreds of hours of audio. We aim to understand how our restoration and land management practices are impacting biodiversity, Lessons learned can help us improve our methods and find new, innovative ways to enhance the quality of wildlife habitats and restore native species. Once collected, the recordings are downloaded and analyzed using specialized software that visually maps the audio into spectrograms—a kind of visual fingerprint of the sounds. From there, trained team members and bioacoustics partners use pattern recognition, call libraries, and sometimes AI-assisted tools to identify species-specific vocalizations. Think of it as decoding a secret language of the wild, or Shazam for wildlife.  

This process helps us track indicator species—wildlife whose presence signals environmental quality or change. The call of a bobolink (Dolichonyx oryzivorus) or eastern meadowlark (Sturnella magna) might tell us a grassland restoration is succeeding, while the seasonal song of the wood thrush (Hylocichla mustelina) offers insight into forest health. Bobolinks and eastern meadowlarks are grassland obligates, they require large, open fields of native grasses for nesting and foraging, making them especially vulnerable to habitat loss and fragmentation. Both species have experienced steep population declines across their range, and in New Jersey, they are considered species of special conservation concern due to the rapid disappearance of grassland habitat. Similarly, the wood thrush depends on mature deciduous forests with rich understory layers. It has declined significantly due to forest fragmentation and habitat degradation and is also listed as a species of concern in the state. 

By monitoring these vocal indicators, we gain crucial insight into the effectiveness of our land management efforts and the broader ecological integrity of our landscapes. As we continue to innovate in how we care for this living landscape, bioacoustics has become one of the most exciting tools in our conservation toolbox—one that reminds us that every chirp, croak, buzz, and birdsong is a signal worth tuning into. 

Examples of Bioacoustic Projects at Duke Farms 

Grassland birds in restored grasslands 

One of our key bioacoustic monitoring projects focuses on assessing grassland bird populations in our restored meadows and grazing pastures. These grasslands are part of a long-term effort to enhance native biodiversity while integrating regenerative agricultural practices and reseeing parcels of land with native grass mixes. By deploying ARUs across sites with different grazing regimes and reseeding efforts, we’re able to capture breeding-season vocalizations from key indicator species like bobolinks, eastern Meadowlarks, and grasshopper sparrows (Ammodramus savannarum). Comparing these acoustic datasets helps us understand how varying grazing intensity affects bird presence, spatial activity and timing, offering a unique window into how working lands can support both agriculture and biodiversity. These insights guide how we manage grazing rotation and native grassland restoration to benefit both birds and soil health. 

Duke Farms’ Raritan Reforestation Project 

Another application of bioacoustics is in our Raritan River Reforestation site, where decades of ecological degradation are being reversed through a multi-year forest restoration effort. Here, ARUs are placed strategically among young forest plots, monitoring how returning tree cover is influencing habitat suitability for birds and bats. The devices capture the calls of forest-dwelling birds like the Wood Thrush, Eastern Wood-Peewee, Scarlet Tanager, and Yellow-throated Warbler - species that thrive in maturing woodlands.  

At night, ultrasonic microphones record the high-frequency echolocation calls of foraging bats, allowing us to track the return of these important insectivores. These soundscapes give us critical feedback on how effective our restoration work is at rebuilding complex, layered habitats that support a rich community of wildlife. 

Through projects like these, bioacoustics is helping Duke Farms move beyond snapshots of biodiversity toward a more nuanced, temporal understanding of ecosystem recovery.  

Experience the Sounds of Nature at Duke Farms

You don’t have to be in the forest or meadow to hear what nature has to say. At Duke Farms, our bioacoustics monitoring program captures the wild soundscapes of New Jersey—from the bubbling calls of spring peepers to the melodic song of the wood thrush.

Now, you can listen in from anywhere. Whether you're relaxing at home, working, or looking to reconnect with the rhythms of the natural world, our archived recordings and sound clips let you experience biodiversity in real time.

Tune in, slow down, and hear what the land is telling us.


Written by:

Vaulted Oak

July 15, 2025